Well, said Sir Tristram, I know that knight well with the covered shield of azure, he is the king's son of Northumberland, his name is Epinegris; and he is as great a lover as I know, and he loveth the king's daughter of Wales, a full fair lady.
Epinegris seems to make his first appearance in Malory at the Castle Dangerous tournament in the book of Gareth Beaumains. Later, Tristram and Dinadan encounter him while they are in the midst of a discussion about whether or not knights in love make the better fighters. With the words quoted above, among others, Tristram eggs Dinadan on to make the test, Dinadan having boasted about his lack of a lady. After asking,
Sir ... is that the rule of you errant knights for to make a knight to joust, will he or nill?,
Epinegris, the lover, unhorses Dinadan. He appears a little after this in unsuccessful pursuit of Breuse Sans Pitie.
Later still, Palomides finds Epinegris wounded. They tell each other their woes. Palomides complains of his love for La Beale Isoud. Epinegris says his case is much worse, for in the tournament of Lonazep he had won his lady (here, the daughter of an earl) by killing her father and one of his two knights.
The next day, as they reposed by a well, Sir Helior le Preuse came, challenged, and fought Epinegris, defeating him and winning away the lady. Palomides brings Epinegris safe to a hermitage, then finds Helior, wins back the lady, defends her against yet another challenger (who turns out to be Palomides' brother Safere), and returns her to Epinegris.